Method of making color photographic film embossing tools



July 7, 1931. H. E. HASTINGS 1,813,669

MMMM OD OF MAKING COLOR PHOTOGRAPHIC FILM EMBOSSING TOOLS Filed NOV. 2, 1923 HenryEHa'siiqga W'Pw latented July 7, 1931 UNITED STATES PATENT OFFICE HENRY E. HASTINGS, OF ROCHESTER, -NEW YORK, ABSIGNOR TO EASTMAN KODAK COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK METHOD OF HAKING COLOR PHOTOGRAPHIC FILM EMBOSSING TOOLS Application med November 2, 1928. Serial No. 316,647.

This invention relates to embossing tools and particularly to embossing rollers for producing minute lenticular elements on film for color photography. One object of my invention is to provide an embossing tool in the form of a roller having microscopic serrations of the same shape and dimensions. Another object is to provide highly polished accurately formed serrations. Another object is to provide a tool which can be manufactured at a reasonable price. Still another object is to provide a method of manufacturing the embossing roller and other ob ects will appear hereinafter from the following specification the novel features bein particularly pointed out in the claims at t e end thereof.

In motion picture color photography,' a

film is sometimes used having minute lenticular elements through which light rays pass to a light sensitive emulsion. These lenticular elements are very small, being in a preferred type about .0018 of an inch in width, although this" dimension may vary considerably in either direction. For best results more than 400 of these lenticular elements should be used to an inch.

In spite of the very small size of these lenslets, they must be accurately formed,

each must be of the same focal length,-the

transparency of the film must not be impaired, the lenslets must remain permanently in the film, and they must be made with consistent uniformity. Such conditions are not easily fulfilled.

To accomplish the desired end the tool used for embossing or knurling the film must be equipped with the same sized serrations as the desired lenslets, the serrations must be perfectly formed, they must be of accurate dimensions, have a high polish and preferably should withstand considerable wear.

The tool which will be hereinafter fully described has been designed to accomplish the above requirements. Coming now to the drawings wherein like reference characters denote like parts throughout:

Fig. 1 is a pers ective view of a roller constructed in accor ance with and illustrating a preferred'form of my invention;

Fig. 2 is a side elevation of a preferred type of hub member;

Fig. 3 is a side elevation of a bronze ring which is to be assembled upon the hub;

Fig. 4 is a side elevation of part of the hub and ring assembled; and

Fi 5 is an enlarged sectional view showing t e serrations magnified many times, so as to illustrate clearly the shape and construction of the serrations.

I prefer to construct an embossin roller by the following method: A steel hu member 1 is first formed by turning very accurately a smooth periphery 2 on an annulus such' as shown in Figure 2. This forms a solid support for the bronze ring 3 which is sweated or pressed into place.

The forming and ingredients of the bronze ring are very im ort-ant, as I have found by trial and error tiiat the finest workmanship can only be done with a specially prepared and treated metal.

The bronze ring is of the best quality phosphor bronze, and I have found that the ollowing formula is especially suitable: copper, 96 parts; tin, 4 parts; and phosporus, 1/500 of one part. p,

This bronze is then prepared by drawing until the commercial grade of hard drawn bronze results, after which it is made still denser and harder by additional drawings. I have found sections of bronze pipe repeatedly drawn and prepared as above described most desirable since this has no seams and is as uniform as I have been able to obtain.

. The final drawing produces a bronze annulus or ring 3 which may conveniently be, when accurately turned, about of an inch thick. This is cut as wide as the hub 1 and is preferably pressed onto the hub, although it may be sweated into place.

This assembly is then placed in a special machine (to form the subject matter of another application) and the surface 4 is carefully trued up-and is then polished by a round diamond point A diamond cutting tool is then used to serrate the polished surface 4. and this tool may be constantly moved by special apparatus to produce a thread like out having sharp edges 5, grooves 6 and angularly disposed walls 7,

or the tool may be moved .0018" (or other desired amount) to produce 'a plurality of circular grooves. This latter type is pre- 5 ferred.

Rollers of high quadity cannot successfully be made of the ordinary bronze, steels, r br'asses of various formulas for the following reasons: Steel is not uniformindensity, has flaky spots and cannot be prepared with the necessary high gloss or polished finish. A number of grooves may be good, but one poor groove spoils the entire cylinder. Brass almost invariably has blow-holes and soft 15 spots and is not readily out perfectly.

Applicant is aware of the fact that all the metals above referred to are considered desirable for much fine work, and wants it understood that many of the imperfections herein referred to are microscopic ones, and for the most part are not visible to the naked eye. It should also be noted that serrations of from .0010 to .0020 of an inch are extremely minute but these can be measured and viewed satisfactorily through a high power microscope, giving, for instance, four hundred magnifications.

The serrations 5, 6 and 7, cut with a diamond tool have a surface of high gloss when out into the bronze mentioned above, and this surface is entirely suitable for a layer 8 of chromium, which produces a highly glossy, hard, non-corroding long wearing surface. Over 250,000 feet of film has been run over a single cylinder without the latter showing signs of deterioration.

Because of the very minute differences between the points and grooves 6say perhaps about .0018 of an inchthese serrations can be successfully plated.

With an embossing cylinder as above described, rounded lenticular elements can be accurately formed, as fully set forth in my copending application for method and apparatu-sfor forming lenticular film' for color photography, Serial No. 316,646, filed November 2, 1928.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The method of preparing an embossing tool for photographic film having minute lenticular areas thereon comprising preparing an extra hard drawn phosphor bronze member with a smooth accurately dimensioned periphery, polishing said periphery, cutting a plurality of closely spaced serrations in the order of .0018 of. an inch in size into the polished periphery, the cutting operation also polishing the serrations, and electro-depositing on the polished serrations a thin layer of chromium.

2. The method of preparin an embossing tool for photographic film having minute lenticular areas thereon comprising preparing an extra. hard drawn phosphor bronze rin and polishing the periphery thereof wit a diamond, cuttin minute grooves in the polished surface w1th a diamond, said ooves being of the order of .0018 of an inch 1n width, and lying adjacent each other over the surfaceof the ring, and electro-plating a very thin layer of'chromium thereon preserving accurately the contour of the serrations.

3. The method of preparing an embossing tool for photographic film, said tool havin minute, highly polished, hard serrations o l the order of .0018 of an inch in width, which consists in preparing a steel core of accurate dimensions, attaching thereto an annular bronze ring the constituents of which are 96 parts copper, 4 parts tin, 1/500 of one part phosphorus, turning said ring accurately to size, polishing the outer surface of the ring with a diamond, cutting a plurality of minute grooves of the order of .0018 of an inch from one to another in the polished bronze ring, producing a highly finished surface thereon, and electroplating a thin coatto ing of chromium on the serrations.

Signed at Rochester, N. Y., this 29th day of October 1928.

HENRY E. STIN GS. 

